Percussion rock-drill.



No. 890,012. R. H, ANDERSON, PATENTED JUNE 9, 1908. PERCUSSION ROCK DRILL.

APPLICATION FILED JAN. 23, 1908 Cir PATENT @Fllilttllfl.

ROBERT HUTCHISON ANDERSON 'OF JOHANNESBURG, TRANSVAAL.

PERCUSSION ROCK-DRILL.

' Application filed T 0 all whom it may concern:

Be it known that l, ltonnnr HU'rcmsoN ANnnnsoN, a citizen of the United States, residing at Marlborough llouse, Doornfontein, Johannesburg, in the colony of the lransvaal, have invented :1 new and useful Improvement in ercussive Roch-Drills, of which the following is a specification.

The present invention relates to percussive rock drills of the general type wherein a plurality of more or less radial cutting edges are separated by spaces for the passage of broken rock and wherein the peripheral sur faces adjacent to the cutting edges form guide faces for the drill.

Such drills have hitherto as a rule been constructed with the cutting edges symmetrically disposed, with the result that al though the drill is rotated to prevent its constantly striking upon the same spot, the edges still tend to a great extent to follow one another, or in other words, any one edge tends to strike in the notch produced by a preceding edge. This impairs the rate of drilling and produces rilling of the hole, the cross section of which becomes a polygon having one more side than there are symmetrically disposed cutting edges on the drill.

In a prior application (Serial No. 355982) I have described a drill in which the points of the cutting edges, (by which the bulk of the cutting is effected and which determine the shape of the hole), are unequally spaced, thus giving the equivalent as far as the prevention of riding is concerned, of a bit hav ing a very large number of cutting edges; and increasing the efficiency of the drill by causing the cuts'to be distributed widely over the rock face as the drill rotates. in such drill however, the angle of the cutting edges is uniform, and the peripheral guiding surfaces formed by the outer ends thereof as mentioned above, are unequally spaced, which somewhat impairs the guiding of the drill.

It is the object of the present invention to provide a drill in which the points of the cutting edges are unequally spaced as in my prior invention, but in which the guiding is improved by reason of the guiding faces being equally spaced; and in which also the angles of the several cutting edges are unequal, or differently disposed, thereby producing certain advantages in operation as hereafter mentioned.

Specification of Letters Patent.

January 23, 1908.

Patented Mine 9, 1908.

Serial No. 412,357.

In the accompanying drawing Figure I is a perspective view of the improved bit, and Fig. 11 a plan of the same; Figs. 1H, 1V and V, are projections of the guiding surfaces thereof, and Figs. V1 and Yll illustrate a feature in the operation of the drill.

The drill here illustrated is of the general type described in my prior application wherein a detachable drill cap comprises a body portion a and raised cutting edges b, e, d, formed integral therewith. The cap is adapted to be secured to a permanent shank by means of a tie rod having a triangular tapered head which "fits into the corresponding hole a in the cap.

The drill has preferably three cutting l edges 1), c, and 1, of which the points I), c, l and (7. respectively are unequally spaced; there being in the present case an angle of 100 between I) and c 135 between c and c and 125 between at and b. The edges "may be radial in plan as in the ordinary i drills; or they may be irregularly disposed l as shown, for the purpose of diminishing the tendency of any part of one edge to follow the preceding edge. The points of the edges are preferably disposed in advance of the central parts thereof with the object of assisting the rock to burst inwardly to the center when struck.

f, g, and 71, are the guiding faces, which are equidistant from the center of the drill and are disposed symmetrically around the periphery thereof. Such symmetry of the guiding faces combined with the asymmetry of the points causes the respective angles of the edges to be dissimilarly disposed and usually also unequal in magnitude.

As seen in Figs. lll, TY, and Y, the angle of the edge d is symmetrically disposed with drill, while those 1 reference to the axis of the l of the other edges are, as it were, tilted, but \in opposite directions. As illustrating the effect of this arrangement in cutting the rock, Fig. VI represents the edge (1 punched into the rock and forming therein a correspending V notch. fore the cutting angles all similar, a following cutter which ha l the same place wou d l exactly fit the notch, and, making contact with the whole surface thereof, would require l to cause it to penetrate. On the other hand supposing the edge 0 of the resent drill to follow, it would make contact with the rock at two points only, as seen in ened to strike in considerable force rality of cutting edges, guiding faces formed F metrically arranged and the guiding faces being symmetrically arranged.

2. A percussive rock drill having a plurality of cutting edges and guide faces formed at the peripheral extremities thereof; the points of the cutting edges being unsymmetrically arranged, the guide faces being 30 Fig. V II, in Which penetration is supposed to have begun. The blow is thus concen trated and produces a correspondingly better result; for example the large corner of rock on the left hand side of Fig. VII is readily broken off and at the same time the penetration of the point of the cutter is comparatively unimpeded. l symmetrically arranged and the angles of the It is to be understood that although the cutting edges being differently disposed relainvention has been described and illustrated tively to the axis of the drill. only iii connection with a drill of the type 3. In a percussive rock drill a plurality of comprising a complete detachable head, to cutting edges and a plurality of guiding faces which it is evidently for manufacturing readisposed at the peripheral extremities theresons most readily applicable, it may neverof, said cutting edges being unequally spaced theless be applied to drills having a plurality l and said guiding faces being equally spaced, of detachable cutters or to solid drills having I substantially as described. the cutting parts forged on the shank. In testimony whereof I affix my signature 40 \Vhat I claim as my invention, and desire in presence of two witnesses.

to secure by Letters Patent, 1s.' T T r 1. A percussive rock drill having a plut ROBLM HUTOHIWA MDERSOA' \Yitnesses:

ALFRED L. SPooR, lVEsLnY E. JOHN.

at the peripheral extremities thereof; the points of the cutting edges being unsym- 

